FBV3 expression pedal died. in FBV Controllers (MKI / MKII / 3) Posted May 23, 2020 17 hours ago, saracen22 said: maybe someone knows what is this element? Q1? Hi. The chip labelled Q1 is a photo-receptor. The LED D1 shines light at a constant level which is reflected by the white flag attached to the pedal and the amount of reflected light (as per the inverse square law) is detected by the detector Q1. Have you tried using a torch to shine on the Q1 detector? If you do that and see the Wah/Vol parameter change as you waft the torch over it, you will know if the detector circuitry is working and that it's the LED at fault. If not... then I guess you have bigger problems. If you have replaced the LED D1, does it light up? If not you could have put it in the wrong way round or maybe over heated it with the soldering iron. Michael.